The objective of the proposed research work is: (a) to apply a new method to estimate albumin synthesis in elderly human subjects. The method most commonly used to date involves the use of a 14C label and this procedure is limited to individuals over 35 years of age. The methodology proposed in this research project will utilize the stable isotope of nitrogen (15N). Consequently, the method can be used to estimate albumin synthesis in all age groups, allowing a critical assessment of the effect of progressive aging on albumin synthesis in the human; (b) to refine previous studies conducted by us on whole body protein turnover in elderly and young adult subjects. These studies will examine whole body protein metabolism and rates of albumin synthesis in elderly subjects and young adults given varying levels of dietary protein intake. The purpose is to obtain a more complete understanding of the nature of body protein metabolism, how it changes with increasing adult age and responds to dietary alterations. The longer-term objective is to evaluate more critically the protein needs of the elderly population and factors which affect them.